TCR libraries

1. A library of particles displaying a plurality of different T cell receptors (TCRs), wherein the plurality of TCRs consists essentially of TCRs comprising

(a) an alpha chain, the alpha chain comprising an alpha chain variable domain (Vα) that is a TRAV12-2 gene product from a natural repertoire of TCRs that have undergone thymic selection in a human donor, and

(b) a beta chain, the beta chain comprising a beta chain variable domain (Vβ) that is a gene product of a TRBV gene from a natural repertoire of TCRs that have undergone thymic selection in a human donor,

wherein the Vα CDR3 length varies among the plurality of displayed TCRs and the Vβ CDR3 length varies among the plurality of displayed TCRs,

wherein the TCRs are covalently linked to the particles, and

wherein the particles are phage particles, ribosomes, yeast cells or mammalian cells.

2. The library of claim 1 , wherein the TRBV gene is one of:

TRBV1

TRBV2

TRBV3-1

TRBV3-2

TRBV4-1

TRBV4-2

TRBV4-3

TRBV5-1

TRBV5-2

TRBV5-3

TRBV5-4

TRBV5-5

TRBV5-6

TRBV5-7

TRBV5-8

TRBV6-1

TRBV6-2

TRBV6-3

TRBV6-4

TRBV6-5

TRBV6-6

TRBV6-7

TRBV6-8

TRBV6-9

TRBV7-1

TRBV7-2

TRBV7-3

TRBV7-4

TRBV7-5

TRBV7-6

TRBV7-7

TRBV7-8

TRBV7-9

TRBV8-1

TRBV8-2

TRBV9

TRBV10-1

TRBV10-2

TRBV10-3

TRBV11-1

TRBV11-2

TRBV11-3

TRBV12-1

TRBV12-2

TRBV12-3

TRBV12-4

TRBV12-5

TRBV13

TRBV14

TRBV15

TRBV16

TRBV17

TRBV18

TRBV19

TRBV20-1

TRBV21-1

TRBV22-1

TRBV23-1

TRBV24-1

TRBV25-1

TRBV26

TRBV27

TRBV28

TRBV29-1

TRBV30

3. The library of claim 1 , wherein the framework region, CDR1, CDR2, and/or CDR3 sequence of the alpha and/or beta variable domain comprises a non-natural mutation.

4. The library of claim 1 , wherein the alpha chain variable domain and the beta chain variable domain are displayed as a single polypeptide chain.

5. The library of claim 1 , wherein the TCRs comprise a non-native disulfide bond between a constant region of the alpha chain and a constant region of the beta chain.

6. The library of claim 1 , wherein the TCRs comprise a native disulfide bond between a constant region of the alpha chain and a constant region of the beta chain.

7. The library of claim 1 , wherein each alpha chain and each beta chain comprises a dimerization domain.

8. The library according to claim 7 , wherein the dimerization domain is heterologous.

9. The library of claim 1 , wherein the particles are phage particles.

10. The library of claim 1 , wherein the particles are ribosomes.

11. The library of claim 1 , wherein the particles are yeast cells.

12. The library of claim 1 , wherein the particles are mammalian cells.

13. A method of obtaining a T cell receptor (TCR) that specifically binds a peptide antigen, comprising screening the library of phage particles of claim 9 with the peptide antigen, the method comprising:

a) panning the library using as a target the peptide antigen;

b) repeating step a) one or more times;

c) screening the phage particles identified in step a) or b); and

d) identifying a TCR that specifically binds the peptide antigen.

14. A method of making the library of particles of claim 1 , the library displaying a plurality of different TCRs, the method comprising:

i) obtaining from a natural repertoire a plurality of nucleic acids that encode different TRAV12-2 alpha chain variable domains;

ii) obtaining from a natural repertoire a plurality of nucleic acids that encode different TRBV beta chain variable domains of a TRBV gene;

iii) cloning the TRAV12-2 alpha chain variable domain encoding nucleic acids into expression vectors;

iv) cloning the TRBV beta chain variable domain encoding nucleic acids into the same or different vectors; and

v) expressing the vectors in particles, thereby generating a library consisting essentially of TCRs comprising an alpha chain variable domain and a beta chain variable domain encoded by the nucleic acids.

15. A method of making the library of particles of claim 1 , the library displaying a plurality of different TCRs, the method comprising:

i) obtaining a plurality of nucleic acids that encode different TRAV12-2 alpha chain variable domains using primers that hybridize to nucleic acids encoding TRAV12-2 alpha chain variable domains;

ii) obtaining a plurality of nucleic acids that encode different beta chain variable domains at a TRBV using primers that hybridize to nucleic acids encoding the TRBV beta chain variable domains;

iii) cloning the TRAV12-2 alpha chain variable domain encoding nucleic acids into expression vectors;

iv) cloning the TRBV beta chain variable domain encoding nucleic acids into the same or different vectors; and

v) expressing the vectors in particles, thereby generating a library consisting essentially of TCRs comprising an alpha chain variable domain and a beta chain variable domain encoded by the nucleic acids to which said primers hybridize.

16. The method of claim 14 , wherein the particles are phage particles; and the primers that hybridize to nucleic acids encoding TRAV12-2 alpha chain variable domains consist of SEQ ID NOS: 2, 11, 13, and 14; and the primers that hybridize to nucleic acids encoding TRBV beta chain variable domains comprise of SEQ ID NOS: 1, 3-10, 12, and 15; and the expression vectors are pIM672.